Bidirectional power management techniques

ABSTRACT

Power management techniques are disclosed. For instance, an apparatus may include a bidirectional voltage converter circuit, and a control module that selectively operates the bidirectional voltage converter circuit in a charging mode and a delivery mode. The charging mode converts a voltage provided by an interface (e.g., a USB interface) into a charging voltage employed by an energy storage module (e.g., a rechargeable battery). Conversely, the delivery mode converts a voltage provided by the energy storage module into a voltage employed by the interface.

BACKGROUND

Mobile devices, such as smart phones and personal digital assistants(PDAs), may provide various processing capabilities. For example, mobiledevices may provide users with Internet browsing, word processing,spreadsheets, synchronization of information (e.g., e-mail) with adesktop computer, and so forth.

A typical mobile device includes a battery that delivers power tocomponents within the mobile device. Also, the battery may provide powerto attached devices. Furthermore, the battery may be charged by suchattached devices. Connections with attached devices may be providedthrough various interfaces. Such interfaces may provide media (e.g.,conductive line(s), wireless channels, etc.) for the transfer ofinformation as well as power. Universal Serial Bus (USB) is an exampleof such an interface.

Often, size and cost are important reductions are important design goalsfor devices. Accordingly, it may be desirable to reduce the cost andsize of components that exchange power between attached devices andenergy storage components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an apparatus embodiment.

FIGS. 2 and 3 are diagrams showing implementation embodiments.

FIG. 4 is a flow diagram.

FIG. 5 is a diagram of a system embodiment.

DETAILED DESCRIPTION

Various embodiments may be generally directed to power managementtechniques. For instance, an apparatus may include a bidirectionalvoltage converter circuit, and a control module that selectivelyoperates the bidirectional voltage converter circuit in a charging modeand a delivery mode. The charging mode converts a voltage provided by aninterface (e.g., a USB interface) into a charging voltage employed by anenergy storage module (e.g., a rechargeable battery). Conversely, thedelivery mode converts a voltage provided by the energy storage moduleinto a voltage employed by the interface. Embodiments may advantageouslyprovide size and cost reductions over conventional arrangements thatprovide separate circuits for charging and delivery modes of operation.

Embodiments may comprise one or more elements. An element may compriseany structure arranged to perform certain operations. Each element maybe implemented as hardware, software, or any combination thereof, asdesired for a given set of design parameters or performance constraints.Although an embodiment may be described with a limited number ofelements in a certain topology by way of example, the embodiment mayinclude other combinations of elements in alternate arrangements asdesired for a given implementation. It is worthy to note that anyreference to “one embodiment” or “an embodiment” means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment. The appearances ofthe phrase “in one embodiment” in various places in the specificationare not necessarily all referring to the same embodiment.

FIG. 1 is a diagram of an apparatus 100 that may employ techniquesdescribed herein. Apparatus 100 may include various elements. Forinstance, FIG. 1 shows apparatus 100 including an interface module 102,an energy storage module 104, a power distribution module 106, and apower management module 108. These elements may be implemented inhardware, software, firmware, or any combination thereof.

Apparatus 100 may be included in a mobile communications device, such asa smartphone, a PDA, or a mobile interface device (MID). However,apparatus 100 may be included in other types of devices, such as alaptop computer, a desktop computer, and so forth. The embodiments,however, are not limited to these examples.

Interface module 102 provides for the exchange of information withattached devices (e.g., external devices). Also, interface module 102provides for the flow of power. This flow of power may be to or fromsuch attached devices. Exemplary attached devices include jump drives,computing devices (e.g., desktop and laptop computers), printers,modems, and various peripheral devices. In addition, such attacheddevices may include a power adapter that provides power (e.g., power ata DC voltage) to apparatus 100. However, other types of attached devicesmay be employed.

In embodiments, interface module 102 may provide for connections withsuch attached devices through a universal serial bus (USB) interface.USB interfaces employ a twisted pair data cable to transmit signals.This twisted pair includes a first signal line called D+, and a secondsignal line called D−. In addition, a USB interface provides a singleline for the transfer of power. In accordance with USB standards, thispower line operates at 5 volts DC (within a tolerance of ±5%).

Although a USB interface is described herein, embodiments are notlimited to employing such interfaces. Moreover, embodiments are notlimited to interfaces that employ power at 5 volts DC.

Energy storage module 104 stores energy that may provide operationalpower to components within apparatus 100, as well as to attached devices(e.g., devices connected through interface module 102). Accordingly,energy storage module 104 may comprise one or more batteries and/orcells implemented according to various storage technologies. Suchtechnologies may be rechargeable.

For instance, energy storage module 104 may comprise a rechargeablelithium ion (Li-ion) battery having a cell voltage between 3.0 volts and4.2 volts. However, other types of technologies may be employed.Examples of such technologies include lead and sulfuric acid, nickelcadmium (NiCd), nickel metal hydride (NiMH), lithium ion polymer (Li-ionpolymer), and so forth.

Accordingly, in embodiments, interface module 102 and energy storagemodule 104 may employ different operational voltages. For instance,interface module 102 may employ a 5 volt USB interface and energystorage module 104 may employ a 3.0 volt to 4.2 volt Li-ion technology.Apparatus 100, however, is not limited to this implementation. Thus,other combinations of operational voltages may be employed.

As described above, apparatus 100 may be included in a device (e.g., amobile communications device, etc.). More particularly, apparatus 100may be included in a device's motherboard. However, embodiments are notlimited to this arrangement. Power distribution module 106 provides forthe distribution of power to such a device's components. Thesecomponents may require different operational voltages. Accordingly,power distribution module 106 may include one or more DC to DC convertercircuits. In embodiments, power distribution module 106 may operate onvoltage provided by energy storage module 104, as well as on voltagesprovided by interface module 102 (e.g., from attached devices).

Power management module 108 manages the flow of power for apparatus 100.In particular, power management module 108 may direct apparatus 100 tooperate according to various modes regarding the transfer of power.Examples of such modes include a delivery mode and a charging mode.

In the delivery mode, power flows from battery 104 (or other operationalpower source provided by apparatus 100) to an attached device throughinterface module 102. However, in the charging mode, power flows frominterface module 102 to battery 104.

Thus, power management module 108 provides for the bidirectional flow ofpower. In embodiments, this feature is provided through a bidirectionalvoltage converter circuit within power management module 108. Asdescribed above, conventional approaches employ separate conversioncircuits: a circuit for charging mode, and a circuit for delivery mode.Accordingly, embodiments may advantageously provide cost and sizesavings.

FIG. 2 is a diagram of an implementation 200 that may be included inpower management module 108. Implementation 200 may include variouselements. For instance, FIG. 2 shows implementation 200 including abidirectional voltage converter circuit 202 and a control module 204.Also, implementation 200 is shown including switching elements 206 a-d.

For purposes of illustration, implementation 200 is shown being coupledto elements of FIG. 1 (interface module 102, energy storage module 104,and power distribution module 106). For instance, implementation 200 maybe coupled to a power line of interface module 102 (e.g., a USB powerline). Also, implementation 200 may be coupled to a terminal (e.g., ananode) of energy storage module 104. Embodiments, however, are notlimited to the context of FIG. 1. Thus, apparatus 200 may be coupled toother elements (e.g., other interfaces, energy storage components,and/or power distribution components).

Bidirectional voltage converter circuit 202 provides conversions betweenvoltages employed by interface module 104 and an energy storage module104. This conversion may be in either direction. For instance,bidirectional voltage converter circuit 202 may convert a voltageprovided by energy storage module 104 into a voltage employed byinterface module 102. Conversely, bidirectional voltage convertercircuit 202 may convert a voltage provided by interface module 102 intoa charging voltage employed by energy storage module 104. The manner anddirection of such conversions is directed by control module 204.

As shown in FIG. 2, bidirectional voltage converter circuit 202 includesa first switching element 208, a second switching element 210, and aninductance 212. FIG. 2 shows that switching elements 208 and 210 may beimplemented as metal oxide semiconductor field effect transistors(MOSFETs). In particular, switching element 208 is shown as a P-channelMOSFET, while switching element 210 is shown as an N-channel MOSFET.However, other types of devices may be employed.

In particular, FIG. 2 shows switching element 208 coupled between a nodeN1 and a node N2. In turn, switching element 210 is coupled between nodeN2 and a node N3. Finally, inductance 212 is coupled between node N2 anda node N4. As shown FIG. 2, node N3 may be a ground node.

As described above, control module 204 directs the conversion ofvoltages by bidirectional voltage converter circuit 202. In particular,control module 204 generates control signals 220 c and 220 d to controlswitching elements 208 and 210 within bidirectional voltage convertercircuit 202. These control signals establish whether the correspondingswitching elements are in an ON (closed) state or an OFF (open) state.

As, described above, implementation 200 includes switching elements 206a-d. FIG. 2 shows these elements being implemented as MOSFETs. However,other types of devices may be employed. Control module 204 operatesswitching elements 206 a, 206 b, 206 c, and 206 d through controlsignals 220 a, 220 b, 220 e, and 220 f, respectively. These controlsignals establish whether the corresponding switching elements are in anON state or an OFF state.

The manner in which control signals 220 a-e are generated is based on amode of operation of implementation 200. Such modes include a chargingmode and a delivery mode. Control module 204 may select among such modesbased on information 222 obtained from interface module 102. Controlsignal 220 f is generated based on whether power distribution module 106is to deliver power to various components. For instance, control signal220 f may place switching element 206 d in an ON state to deliver suchpower. This may be based on a user selection and/or on automatic powerdelivery procedures. Control module 204 may be implemented in hardware,software, firmware, or any combination thereof.

The charging mode involves power flowing from an attached device throughinterface module 102. More particularly, control module 204 employsswitching techniques that convert a voltage employed by interface module102 to a voltage employed by energy storage module 104. As a result ofthis flow of power, energy storage module 104 may be charged.

In the charging mode, control module 204 sets switching elements 206 a-din a way such that power provided by an attached device (coupled tointerface module 102) charges energy storage module 104 (throughbidirectional voltage converter circuit 202). Details regarding thesetting of these switches are provided below in greater detail.

Within bidirectional voltage converter circuit 202, switching element208 connects the power provided from the attached device (throughinterface module 102) to inductance 212 in a chopped mode at aparticular frequency. An exemplary frequency is 300 kHz. However, otherfrequencies may be employed.

During times when switching element 208 is in an ON state, current flowsfrom interface module 102 to inductance 212 and ramps up to a neededcharging current (this occurs during constant-current time). However,during times when switching element 208 is in an OFF state, switchingelement 210 is placed in an ON state (this may occur a short timeinterval after switching element 208 is placed in an OFF state). Thisturning on of switching element 210 is performed to keep current flowingthrough inductance 212. While switching element 210 is in the ON state,the current through inductance 212 may ramp down from a positive peakvalue to a minimum value.

This switching of elements 208 and 210 may continue at the frequency(e.g., 300 kHz) until battery 104 is completely charged. At this point,switching elements 208 and 210 may both be placed in the OFF state. Theswitching characteristics (e.g., frequency and duty cycle) of switchingelements 208 and 210 may be selected to provide energy storage module104 with a regulated charging voltage level.

Unlike the charging mode, the delivery mode involves power flowing fromenergy storage module 104 (or other power source) to an attached devicethrough interface module 102. More particularly, control module 104employs switching techniques that convert the voltage of energy storagemodule 104 to the voltage employed by interface module 102.

In the delivery mode, control module 204 sets switching elements 206 a-din a way that power provided by energy storage module 104 is delivered(through bidirectional voltage converter circuit 202) to a device thatis coupled to interface module 102. In addition, these switchingelements are set to deliver power from energy storage module 104 topower distribution module 106. Details regarding the setting of theseswitches are provided below in greater detail.

Within bidirectional voltage converter circuit 202, switching elements208 and 210 behave differently in the delivery mode than in the chargingmode. For instance, switching element 210 behaves as a primary switchingdevice. Thus, switching element 210 connects the power provided fromenergy storage module 104 to inductance 212 in a chopped mode at aparticular frequency. An exemplary frequency is 300 kHz. However, otherfrequencies may be employed.

When in an ON state, switching element 210 connects inductance 212 toground. As a result, the voltage level of energy storage module 104causes current through inductance 212 to ramp up. However, the currentof inductance 212 flows through the body diode of switching element 208when switching element 210 is in an OFF state. As described above,switching element 208 may be implemented as a P-channel MOSFET. Throughthis feature, the current of inductance 212 flows through its body-diodeto interface module 102.

In embodiments, switching element 208 may be placed in an ON stateduring the time that its body-diode steers current from inductance 212to interface module 102 (i.e., when switching element 210 is in an OFFstate). This may advantageously reduce power loss in the body diode andprovide a more efficient voltage conversion.

The switching characteristics (e.g., frequency and duty cycle) ofswitching element 210 may be selected to provide an attached device witha regulated voltage level employed by interface module 102.

FIG. 2 shows that control module 204 receives information 222 frominterface module 102. This information conveys characteristics regardinga device attached through interface module 102. For example, suchcharacteristics may include whether the attached device provides poweror needs power. Based on this information, control module 204 determinesan operational mode (e.g., delivery mode or charging mode). In addition,control module 204 may determine operational parameters based oninformation 222. Such operational parameters may include settings forswitching elements 206 a-206 d. In addition, such operational parametersmay include switching characteristics (frequency, duty cycle, timing,etc.) of switching elements 208 and 210 within bidirectional voltageconverter circuit 202.

As described above, control module 204 sets switching elements 206 a-daccording to whether the delivery mode or the charging mode is beingemployed.

For example, in the charging mode, switching element 206 a is set in anON state to deliver power from interface module 102 to bidirectionalvoltage converter circuit 202. Also, switching element 206 b is set inan ON state. This provides for the delivery of power to powerdistribution module 106 (if switching element 206 d is also in an ONstate). Also, in the charging mode, control module 204 sets switchingelement 206 c to an OFF state. This prevents energy storage module 104from delivering power to power distribution module 106 and/or interfacemodule 102.

In the delivery mode, control module 204 sets switching module 206 a inan ON State to deliver power from bidirectional voltage convertercircuit 202 to interface module 102. However, switching module 206 b isset in an OFF state. Also, in the delivery mode switching module 206 cis set to an ON state. This allows for energy storage module 104 todeliver power to power distribution module 106 (if switching element 206d is in an ON state).

FIG. 3 is a diagram of a further implementation 300 that may be includedin power management module 108. Implementation 300 is similar to theimplementation of FIG. 2. However, implementation 300 replaces controlmodule 204 with a control module 204′. Also, implementation 300 replacesswitching elements 206 a-d with switching elements 302 a and 302 b. Asshown in FIG. 3, these switching elements may be implemented as MOSFETs.However, other types of devices may be employed.

Control module 204′ may be implemented in hardware, software, firmware,or any combination thereof. As shown in FIG. 3, control module 204′generates control signals 320 b and 320 c, which operate switchingelements 208 and 210 within bidirectional voltage converter circuit 202.This operation is based on whether implementation 300 is in the chargingor delivery mode. Thus, this control may be in the manner describedabove with reference to FIG. 2.

Further, control module 204′ operates switching elements 302 a and 302b, through control signals 320 a and 320 d, respectively. For instance,control module 204′ sets switching element 302 a in an ON state when adevice is attached to interface module 102. Also, control module 204′sets switching element 302 d in an ON state when power distributionmodule 106 is to deliver power to various components. This may be basedon a user selection and/or on automatic power delivery procedures.

As described above, embodiments may operate with various interface typesand energy storage technologies. Exemplary embodiments employ USBinterfaces that employ 5 volt power lines and Li-ion batteries thatoperate at voltages between 3.0 volts and 4.2 volts. Control modules 204and 204′ may operate switching elements in a manner such thatbidirectional voltage conversion module converts between these voltages.The embodiments, however, are not limited to these interfaces, voltages,or storage technologies.

Operations for the above embodiments may be further described withreference to the following figures and accompanying examples. Some ofthe figures may include a logic flow. Although such figures presentedherein may include a particular logic flow, it can be appreciated thatthe logic flow merely provides an example of how the generalfunctionality as described herein can be implemented. Further, the givenlogic flow does not necessarily have to be executed in the orderpresented, unless otherwise indicated. In addition, the given logic flowmay be implemented by a hardware element, a software element executed bya processor, or any combination thereof. The embodiments are not limitedin this context.

FIG. 4 illustrates one embodiment of a logic flow. In particular, FIG. 4illustrates a logic flow 400, which may be representative of theoperations executed by one or more embodiments described herein. Thisflow is described with reference to FIGS. 2 and 3. However, suchoperations are not limited to these exemplary contexts. Moreover,although FIG. 4 shows a particular sequence of operations, othersequences may be employed. Also, the depicted operations may beperformed in various parallel and/or sequential combinations.

As shown in FIG. 4, logic flow 400 includes a block 402, whichdetermines whether a charging condition occurs. For example, withreference to FIGS. 2 and 3, this may involve control module 204 (or204′) determining whether a device is attached to interface module 102that provides charging power. An example of such a device is a poweradapter. The embodiments, however, are not limited to such devices.

If a charging condition occurs, then operation proceeds to a block 404.At this block, a converter circuit (e.g., bidirectional voltageconverter circuit 202) is operated in a charging mode.

At a block 406, it is determined whether a delivery condition exists.Referring again to FIGS. 2 and 3, this may involve determining whether adevice requiring operational power is attached to interface module 102.An example of such a device is a jump drive. However, the embodimentsare not limited to these devices. If a delivery condition occurs, thenoperation proceeds to a block 408. At this block, the converter circuitis operated in a delivery mode.

FIG. 5 illustrates an embodiment of a system 500. This system may besuitable for use with one or more embodiments, such as apparatus 100,implementations 200 and 300, logic flow 400, and so forth. Accordingly,system 500 may perform power management techniques, such as the onesdescribed herein.

As shown in FIG. 5, system 500 may include a device 502, an attacheddevice 503, a communications network 504, and a remote device 506.Embodiments, however, are not limited to these elements. Device 502 maybe a mobile communications device, such as a smartphone, a PDA, or aMID. However, device 502 may be other types of devices, such as a laptopcomputer, a desktop computer, and so forth. The embodiments, however,are not limited to these examples.

FIG. 5 shows that device 502 may include the elements of FIG. 1.However, device 502 may alternatively include elements of otherembodiments. Also, device 502 may include a processor 507, a memory 508,a user interface 510, and a communications interface 512. These elementsmay be implemented in hardware, software, firmware, or any combinationthereof.

Processor 507 may include one or more microprocessors, microcontrollers.Processor 507 may execute instructions to perform various operations.Such operations may involve user applications, communicationsprocessing, power management operations, and so forth.

Memory 508 may store information in the form of data. For instance,memory 508 may contain application documents, e-mails, sound files,and/or images in either encoded or unencoded formats. Alternatively oradditionally, memory 508 may store control logic, instructions, and/orsoftware components. This may include instructions that can be executedby one or more processors, such as processor 507. Such instructions mayprovide functionality of one or more elements.

It is worthy to note that some portion or all of memory 508 may beincluded in other elements of system 500. For instance, some or all ofmemory 508 may be included on a same integrated circuit or chip withelements of apparatus 100. Alternatively, some portion or all of memory508 may be disposed on an integrated circuit or other medium (e.g., ahard disk drive). The embodiments are not limited to these examples.

Memory 508 may be implemented using any machine-readable orcomputer-readable media capable of storing data, including both volatileand non-volatile memory. For example, memory 508 may include read-onlymemory (ROM), random-access memory (RAM), dynamic RAM (DRAM),Double-Data-Rate DRAM (DDRAM), synchronous DRAM (SDRAM), static RAM(SRAM), programmable ROM (PROM), erasable programmable ROM (EPROM),electrically erasable programmable ROM (EEPROM), flash memory, polymermemory such as ferroelectric polymer memory, ovonic memory, phase changeor ferroelectric memory, silicon-oxide-nitride-oxide-silicon (SONOS)memory, magnetic or optical cards, or any other type of media suitablefor storing information. The embodiments are not limited in thiscontext.

User interface 510 facilitates user interaction with device 502. Thisinteraction may involve the input of information from a user and/or theoutput of information to a user. Accordingly, user interface 510 mayinclude one or more devices, such as a keyboard (e.g., a full QWERTYkeyboard), a keypad, a touch screen, a microphone, and/or an audiospeaker.

Communications interface 512 provides for the exchange of informationwith device 506. This exchange of information may be across one or morewireless or wired connections. For purposes of illustration, FIG. 5shows communications interface 512 providing wireless connectivity todevice 506 through a wireless network 504. Wireless network 504 may be aterrestrial cellular network, a satellite network, a wireless local areanetwork (e.g., a WiFi network), a wireless metropolitan network (e.g., aWIMAX network), as well as other types of networks. Accordingly,communications interface 512 may include various components, such as atransceiver and control logic to perform operations according to one ormore communications protocols.

Communications between device 502 and device 506 may include telephonyand messaging. In addition, such communications may include the exchangeof information, such as e-mail, calendar entries, contact information,application files, content (e.g., audio, image, and/or video), and soforth.

FIG. 5 shows that device 502 is coupled to an attached device 503. Thiscoupling is through interface module 102. Power may flow betweenattached device 502 and energy storage module 104 according to thetechniques described herein.

Numerous specific details have been set forth herein to provide athorough understanding of the embodiments. It will be understood bythose skilled in the art, however, that the embodiments may be practicedwithout these specific details. In other instances, well-knownoperations, components and circuits have not been described in detail soas not to obscure the embodiments. It can be appreciated that thespecific structural and functional details disclosed herein may berepresentative and do not necessarily limit the scope of theembodiments.

Various embodiments may be implemented using hardware elements, softwareelements, or a combination of both. Examples of hardware elements mayinclude processors, microprocessors, circuits, circuit elements (e.g.,transistors, resistors, capacitors, inductors, and so forth), integratedcircuits, application specific integrated circuits (ASIC), programmablelogic devices (PLD), digital signal processors (DSP), field programmablegate array (FPGA), logic gates, registers, semiconductor device, chips,microchips, chip sets, and so forth. Examples of software may includesoftware components, programs, applications, computer programs,application programs, system programs, machine programs, operatingsystem software, middleware, firmware, software modules, routines,subroutines, functions, methods, procedures, software interfaces,application program interfaces (API), instruction sets, computing code,computer code, code segments, computer code segments, words, values,symbols, or any combination thereof. Determining whether an embodimentis implemented using hardware elements and/or software elements may varyin accordance with any number of factors, such as desired computationalrate, power levels, heat tolerances, processing cycle budget, input datarates, output data rates, memory resources, data bus speeds and otherdesign or performance constraints.

Some embodiments may be described using the expression “coupled” and“connected” along with their derivatives. These terms are not intendedas synonyms for each other. For example, some embodiments may bedescribed using the terms “connected” and/or “coupled” to indicate thattwo or more elements are in direct physical or electrical contact witheach other. The term “coupled,” however, may also mean that two or moreelements are not in direct contact with each other, but yet stillco-operate or interact with each other.

Some embodiments may be implemented, for example, using amachine-readable medium or article which may store an instruction or aset of instructions that, if executed by a machine, may cause themachine to perform a method and/or operations in accordance with theembodiments. Such a machine may include, for example, any suitableprocessing platform, computing platform, computing device, processingdevice, computing system, processing system, computer, processor, or thelike, and may be implemented using any suitable combination of hardwareand/or software. The machine-readable medium or article may include, forexample, any suitable type of memory unit, memory device, memoryarticle, memory medium, storage device, storage article, storage mediumand/or storage unit, for example, memory, removable or non-removablemedia, erasable or non-erasable media, writeable or re-writeable media,digital or analog media, hard disk, floppy disk, Compact Disk Read OnlyMemory (CD-ROM), Compact Disk Recordable (CD-R), Compact DiskRewriteable (CD-RW), optical disk, magnetic media, magneto-opticalmedia, removable memory cards or disks, various types of DigitalVersatile Disk (DVD), a tape, a cassette, or the like. The instructionsmay include any suitable type of code, such as source code, compiledcode, interpreted code, executable code, static code, dynamic code,encrypted code, and the like, implemented using any suitable high-level,low-level, object-oriented, visual, compiled and/or interpretedprogramming language.

Unless specifically stated otherwise, it may be appreciated that termssuch as “processing,” “computing,” “calculating,” “determining,” or thelike, refer to the action and/or processes of a computer or computingsystem, or similar electronic computing device, that manipulates and/ortransforms data represented as physical quantities (e.g., electronic)within the computing system's registers and/or memories into other datasimilarly represented as physical quantities within the computingsystem's memories, registers or other such information storage,transmission or display devices. The embodiments are not limited in thiscontext.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

1. An apparatus, comprising: a bidirectional voltage converter circuit; and a control module to selectively operate the bidirectional voltage converter circuit in a charging mode and a delivery mode, the charging mode to convert a voltage provided by an interface into a charging voltage employed by an energy storage module, and the delivery mode to convert a voltage provided by the energy storage module into a voltage employed by the interface.
 2. The apparatus of claim 1, wherein the control module is to operate the bidirectional voltage converter circuit in the charging mode when a device providing charging power is attached to the interface.
 3. The apparatus of claim 1, wherein the control module is to operate the bidirectional voltage converter circuit in the delivery mode when a device requiring operational power is attached to the interface.
 4. The apparatus of claim 1, wherein the bidirectional voltage converter circuit includes a first switching element coupled between a first node and a second node; a second switching element coupled between the second node and a third node; and an inductance coupled between the second node and a fourth node.
 5. The apparatus of claim 4, wherein the first switching element is a P-channel metal oxide semiconductor field effect transistor (MOSFET), and the second switching element is an N-channel MOSFET.
 6. The apparatus of claim 4, wherein the control module periodically switches the first switching element in the charging mode.
 7. The apparatus of claim 4, wherein the control module periodically switches the second switching element in the delivery mode.
 8. A method, comprising: selecting an operational mode from a charging mode and a delivery mode; operating a bidirectional voltage converter circuit in a charging mode when a charging condition occurs, wherein the charging mode converts a voltage provided by an interface into a charging voltage employed by an energy storage module; and operating the bidirectional voltage converter circuit in a delivery mode when a delivery condition occurs, wherein the delivery mode converts a voltage provided by the energy storage module into a voltage employed by the interface.
 9. The method of claim 8, wherein the charging condition comprises a device providing charging power being attached to the interface.
 10. The method of claim 8, wherein the delivery condition comprises a device requiring operational power being attached to the interface.
 11. A system comprising: an energy storage module; an interface; a bidirectional voltage converter circuit; and a control module to selectively operate the bidirectional voltage converter circuit in a charging mode and a delivery mode, the charging mode to convert a voltage provided by the interface into a charging voltage employed by the energy storage module, and the delivery mode to convert a voltage provided by the energy storage module into a voltage employed by the interface.
 12. The system of claim 11, wherein the energy storage module comprises a rechargeable battery.
 13. The system of claim 12, wherein the rechargeable battery is a lithium ion (Li-ion) battery.
 14. The system of claim 11, wherein the interface is a Universal Serial Bus (USB) interface.
 15. The system of claim 11, wherein the control module is to operate the bidirectional voltage converter circuit in the charging mode when a device providing charging power is attached to the interface.
 16. The system of claim 11, wherein the control module is to operate the bidirectional voltage converter circuit in the delivery mode when a device requiring operational power is attached to the interface.
 17. The system of claim 11, wherein the bidirectional voltage converter circuit includes a first switching element coupled between a first node and a second node; a second switching element coupled between the second node and a third node; and an inductance coupled between the second node and a fourth node.
 18. The system of claim 17, wherein the first switching element is an N-channel metal oxide semiconductor field effect transistor (MOSFET), and the second switching element is a P-channel MOSFET.
 19. The system of claim 17, wherein the control module periodically switches the first switching element in the charging mode.
 20. The system of claim 17, wherein the control module periodically switches the second switching element in the delivery mode. 